The invention relates to a method for measuring and/or regulating the oscillation amplitude of an ultrasound oscillator of an ultrasound welding device, comprising components producing and transmitting oscillations in the form of at least one converter and one sonotrode, as well as, if applicable, a booster placed between the converter and the sonotrode, wherein the ultrasound oscillations are produced by transmitting a high frequency voltage coming from a control circuit to the converter. In addition, the invention relates to an ultrasound welding device, comprising components producing and transmitting oscillations in the form of at least one converter and one sonotrode, as well as, if applicable, a booster placed between them, a backing electrode (ambos), between which and the sonotrode compressible, weldable parts, such as wires, are to be placed, preferably in a compression chamber, wherein to the converter for oscillation production an amplitude is transmitted across a control system with high frequency voltage.
In order to obtain reproducible welding results, it is necessary to monitor welding parameters and then, if predetermined target values are exceeded or not met, regulate them. It is thus disclosed in DE-A-198 10 509 to capture ultrasound waves coupling into a welding material following a reciprocal effect with a joined layer as the measuring signal, in order to then further process characteristic parameters by means of a measured data memory and an evaluation unit for the welding process with subsequent control of the sonotrode.
In order to control and regulate the process parameters in the ultrasound welding of plastic parts, DE-A-43 21 874 proposes that the joining force be measured during the welding process to monitor the energy application at a joining location between two parts that are to be welded.
According to EP-B-0 567 426 the oscillation amplitude of a sonotrode welding plastic parts is reduced after a predetermined time interval, in order to then work with a lower oscillation amplitude during the remaining time of the welding operation. An appropriate control signal to reduce the amplitude can also be initiated directly or indirectly as a function of the power transmitted to the work pieces to be welded, as is revealed, for example, in WO-A-1998/49009, U.S. Pat. Nos. 5,855,706, 5,658,408 or 5,435,863.
WO-A-2002/098636 discloses a method for welding plastic parts, in which during an initial time span the oscillation amplitude is reduced following a given course to optimize the welding process, in order to subsequently perform a measurement of a characteristic parameter of the work piece and then, as a function of the value of the parameter measured, end the welding process with a constant amplitude of a sonotrode transmitting ultrasound energy.
In order to check connections established by ultrasonic wire bonding, DE-A-101 10 048 envisions an online monitoring method on the basis of predetermined or stored master values, which allow inferences to be made about the stability of the connection.
An ultrasound welding method for coated electrical wires and a device for performing the method are disclosed in DE-A-102 11 264. In order to vary the welding energy after removal of the insulation and for the welding of the conductors, a measurement of the resistance of the electricity flowing between the sonotrode and the backing electrode is carried out.